1. Field of the Invention
The present invention relates to a flow control device which is operable in several different forms to control fluid flow in pumps particularly of the submersible water well type which conventionally are subject to rapid wear by the presence of particulate matter in the water. The flow control device of the present invention has particular utility in directing the flow of fluid through the pump in a manner which minimizes the destructive effects of such water borne substances as well as of recirculating water and which insures that the operational efficiency of the pump is maintained over an operational life far surpassing that heretofore achieved.
A chronic problem in the use of pumps, particularly of the type used in water wells, is their inability to operate at what theoretically should be their full capacity. Turbulence, recirculating water and the like impede their operation from the outset. These problems are aggravated to a great degree by particulate matter borne by the fluid stream. Although strainers and the like are commonly employed in an effort to remove foreign substances prior to passage through the operative portions of the pumps, it has been found impossible to eliminate much of the particulate matter without reducing pumping capacity below an acceptable level. As a result, the components of such pumps are continuously abraided by sand and the like during operation.
Conventional pump construction contributes further to a complication of these problems. Typically a pump housing is employed which has a constricted throat and an impeller is mounted above but extends into close association with the throat. The impeller is rotated at high speed to achieve the pumping action. A problem inherent in such construction is the recirculation of water about the impeller and back into the throat of the pump. This recirculation is inherently inefficient. However, it also causes turbulence at the throat of the pump and, it is believed, tends further to constrict the flow at that point. The recirculating water carries particulate matter with it. The close tolerance fit of the impeller and the pump housing at this point causes the surfaces thereof rapidly to be worn away which, in turn, increases the volume of water recirculated. This drastically reduces the operating efficiency of the pump. Furthermore, it places stress on the rotating impeller which in turn is transmitted to the drive shaft on which the impeller is mounted. The end result is that all such pumps rapidly wear themselves out and will eventually destroy themselves particularly in areas in which the water bearing formations contain high quantities of sand. Although various seals have been employed in an effort to limit such recirculation, none has heretofore been successful.
As a direct result, such pumps often can be operated for only a few months before becoming so inefficient as to require replacement of the worn components. This, of course, requires that the submersed pump structure be removed from the well which is extremely expensive. Whether operated inefficiently to avoid replacement, or replaced as frequently as needed, such conventional practices are costly to the operator, extremely wasteful of the energy used to operate the pump and result in prolonged "down time" for the pump which is in itself quite expensive.
Therefore, it has long been known that it would be desirable to have a device which maintains the operation of pumps at high efficiency over long operational lives minimizing the destructive effect of particulate matter passing through the pumps, reducing the expense required in maintaining such pumps and insuring that the energy employed in running the pumps is used most efficiently.